Allow users to see all their available branches in the navigation tree

In the navigation tree, when the user does not have access to a workspace, he cannot access this workspace children, except if he is provided with a direct link to this document. In this case, he can navigate up to the first available parent. In our company, this is a problem because we have disabled all the root workspaces access rights for security reason. Our idea here is to provide an access to all the "first available parents", which means all the isolated hierarchies of workspaces can be reached.

Example : in the following hierarchy, the user can only see C in the current version, but cannot access B11 or B2.
A (denied)
+ B (denied)
+ B1 (denied)
+B11 (allowed)
+B111 (allowed)
+B12 (denied)
+ B2 (allowed)
+ C (allowed)

The attached file is a proposed patch to fix this. The user would see this :
B11
B2
C

All documents can be reached this way.

The inconvenience is that the displayed roots are not at the same levels, and if there are many 'holes' the tree can be very crowded.

This has not been fully regression-tested but did not rise any problem in production and is very satisfactory for our user. I provide it for any comment, and is a proposal for a contribution. It is a patch which extends the TreeActionsBean component and overrides the treeActions seam component (with a @Install(precedence = DEPLOYMENT).